To provide solution to the problem of influence from tensioning of the prestressing strands for simply-supported girder and to the optimization of removal of the temporary suspenders and pre-raising amount of the inclination angle of the first segment in the process of span-by-span assembling and erection of precast segments of the prestressed concrete girder bridge, the north approach bridge of Taohuayu Huanghe River Bridge in Zhengzhou on the inner side of the river dyke was cited as an example. The forces of the suspending system formed by the overhead launching gantry, temporary suspenders and concrete main girder for assembling and erection of the precast segments of the bridge were analyzed, using the simplified finite element model that could fulfill rapid calculation and could produce reliable calculation results. The results of the analysis indicate that the tensioning of the prestressing strands for simply-supported girder can cause the main girder to camber inversely and make the force distribution of the temporary suspenders become dramatically worsen, the forces of the midspan suspenders reduced and the forces of the suspenders nearby the girder ends increased. The optimal sequence of removal of the temporary suspenders for system transformation is that the removal should proceed symmetrically from the midspan towards the ends of the girder. Most of the suspenders can be removed in one time while the rest of the suspenders need to relaxed first before removal. The pre-raising amount of the inclination angle of the first segment of the bridge to be constructed by the suspending and assembling technology is 13.6 mm/3.84 m.
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To study the force condition characteristics of the steel and concrete joint section of Jiujiang Changjiang River Highway Bridge, the physical model on a large scale of 1:2 for the joint section with steel cells and rear bearing plates of the bridge was fabricated, tested and the force conditions of the steel structure, concrete box girder, steel cells, U ribs and PBL shear studs and relative slip of the joint surfaces of the steel and concrete of the joint section under the maximum normal bending moment were analyzed. The results of the test and analysis show that the stress of the steel and concrete joint section presents a smooth decrease from the steel girder stiffening section, joint section to the concrete stiffening transition section. The measured maximum compressive stress of the steel structure appears in the bottom plate U ribs, the measured maximum compressive stress of the concrete appears in the top slab with the smallest sectional area and the maximum tensile stress appears inside the bottom plate steel cells. The stress of the shear studs becomes gradually decreased from the locations far from the bearing plates towards the plates, the forces of the webs of the steel cells and the relative slip between the steel and concrete are very little and the measured maximum stress of various parts of the joint section does not exceed the allowable stress values as specified in the codes.
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